Thermoplastic tubes that are formed as squeeze tubes are extensively used in packaging of cosmetics, toothpaste, shampoos, and the like. These tubes are formed as tubular members having an open end at a first end and a threaded or other closure-acceptable head at the second end, with a closure used to seal the second end of the tube while the contents of the tube are charged to the tube through the first end. After filling, the first end of the tube is closed, such as by heat sealing, to complete the filled tube for sale.
A problem has existed in formation of such tubes in that the closure-acceptable head is usually formed separately from the tubular member and provision of a complete seal between the head and tubular member must be assured.
One well known commercial method for producing such headed tubes is that disclosed in U.S. Pat. No. 3,047,910 to M. H. Downs. In this process, a tubular member is placed in a forming collar and a separate molten disc of thermoplastic material forced into an open end of the tubular member while retained by the forming collar. The latent heat of the molten disc welds the peripheral edge of the disc to the inner circumferential wall of the tubular member, and forms an end closure for the tubular member. Pressure is applied to the hot sealed end closure to shape the head into the desired shape and an orifice then formed through the end of the closure. The head is then fitted with a threaded cap or other closure to provide a closed end tube ready for filling with the desired contents for the tube.
In methods such as that disclosed by the Downs, patent, some difficulties remain, such as controlling of the thickness and weight of the head and exact color matching of the tubular member and the head. The Downs, process also can not be used to commercially prepare tubes from polycarbonates and polyvinyl chloride material. Also, any time two separate units such as a tubular member and head are combined, a possible source of weakness exists at the juncture of the two. In addition, with such a juncture, a joint between the tubular member and head, a problem of providing a continuous barrier container is present where the tube is formed of a barrier material, such as from an oxygen-barrier containing composite thermoplastic material.
There have been attempts in the past to produce thermoplastic squeeze tubes by extruding a thermoplastic tubing, cutting the tubing into sleeves or tubular members, heating one end of the sleeve to a molten mass and forming it into a head to make the thermoplastic tube. These methods have not been successful because heat transfer is slow and the molten plastic difficult to control. In such attempts, a sufficient amount of molten thermoplastic cannot be accumulated on the end of the tube to form the desired head.
It is an object of the present invention to provide a method for forming a headed thermoplastic tube solely from a sleeve or tubular member.
It is another object of the present invention to provide a thermoplastic squeeze tube having a head portion that does not have any joint or juncture between the tubular portion of the tube and the head portion thereof.